The statutory number of seats in a parliamentary chamber (defined in the constitution, electoral law or other statutory text) is not always identical to the current number of members of parliament.

The current number may be lower for historical reasons: for example, in Cyprus the 24 seats reserved for the Turkish-Cypriot community remain vacant since the 1960s. It may also be higher than the statutory number where "overhang" seats are foreseen to respect balance in a proportional representation system. Overhang seats can be observed in Germany and New Zealand, for example.